The calibration of your pipettes might be done in two ways:
You calibrate your pipettes in your company.
advantage: time saving; identification of internal interferences and failures; implementation of quick measures; revision of pipette history; detection of drift deviation
disadvantage: additional manpower necessary; high - and partly hidden costs
You send your pipettes to an external laboratory. This laboratory will take over the calibration process.
advantage: saving of manpower
disadvantage: loss of time by the use of additional shipment; double set of pipettes necessary